I need to position several plots below each other and I want the widths of the margin and figure regions to be identical, so they align neatly. Note, that I need two single plots, not one joint plot. I want to save each one in a separate PNG file. I just want their structure (margin, figure region size) to be identical.

@MarkHeckmann ; Baptiste really is the person to help with this. But perhaps expose_layout from his egg package would be useful. So use p1 <- qplot(mpg, wt, data=mtcars, colour=cyl) + ggtitle("facetted plot") ; g = expose_layout(p1) ; g$widths . Then see how the widths align with the exposed layout plot. (widths go from left to right) (also look at names(g) for other things to examine)
– user20650Dec 20 '16 at 15:07